WASHINGTON -- The United States has called on Iran to release Christian pastor Youcef Nadarkhani, who was imprisoned in 2009 and condemned to death for converting from Islam to Christianity.

State Department spokeswoman Victoria Nuland said in a statement that Nadarkhani "still faces the threat of execution for simply following his faith, and we repeat our call for Iranian authorities to release him immediately."

Nadarkhani, 34, converted from Islam to Christianity at the age of 19 and became pastor of a small evangelical community called the Church of Iran.

Nadarkhani's conviction was upheld by an appeals court in September 2010 but overturned by Tehran's supreme court, which sent the case back to the lower court in his hometown of Rasht.